International patent application WO 2006/018749 discloses a near-field optical scanning device for scanning a record carrier. In a near-field optical scanning device a radiation beam is transmitted across a gap between an exit face of an objective system and an outer face of the record carrier using evanescent coupling of the radiation. A gap servo keeps the size of the gap during scanning at a distance of approximately 25 nm.
It is an object of the invention to provide an optical scanning device having an improved performance.